Keep getting error DF-AA-20 on my Android

I keep trying to buy gems but every time I do I get an error from Google Play that reads as follows: "Error retrieving information from server [DF-AA-20]". I tried following all of Google Play's instructions on how to troubleshoot and even contacted Google on the phone, yet I am still unable to fix this.

I keep trying to buy gems but every time I do I get an error from Google Play that reads as follows: "Error retrieving information from server [DF-AA-20]". I tried following all of Google Play's instructions on how to troubleshoot and even contacted Google on the phone, yet I am still unable to fix this.

How can fix this issue?

Dear Leader
Could you tell us your account id and which package you were trying to buy please? Thanks.